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Keep your crop clear of wireworms

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Know these critters to keep them at bay

This season, wireworm control will be top of mind for many farmers, especially the ones I work with in southern Alberta. There’s also a lot of talk about new products coming to market in the next couple of years that will target wireworms. And these could be game changers – advancing from suppression to control.

If you can’t get your hands on that just yet, what’s a wheat grower to do? Understanding the habits and lifecycle of wireworms will help you take action to keep your young crop intact and ultimately protect yield.

Wireworms like free-draining soils with medium texture. Their activity picks up at the same time the crop is emerging and becoming active, threatening young, vulnerable plants.

Here are some frightening facts:

The wireworm population can get to more than 1 million in an acre.

You can have nearly a dozen generations of wireworm in the same field, some hibernating for long periods and more active populations moving up and down in the soil profile as temperatures warm and cool.

Adults (click beetles) emerge in early spring and breed at about 10°C finding places to lay eggs. Larvae emerge later in the crop but will pose little threat until next spring.

Adults prefer to lay their eggs in grassy areas or where there is dense vegetation. Freshly broken ground can have a higher population of wireworms.

Each larva can feed on up to two cereal seeds and together can take down up to 50% of a field.

Larvae can feed on small roots and (below-ground) stems of young plants. Stems appear shredded rather than completely severed.

You likely won’t see the problem until it’s too late to reseed.

Given these habits, I recommend three key actions to minimize the potential damage from wireworms.

Your first order of business is to increase time between cereal crops. Wireworms can go up to two years without food and can survive off humus in the soil. That’s why an extended rotation can be important. Rotate cereals with pulses and canola, which wireworms don’t tend to feed on extensively. No cereal on cereal, or your wireworm population will grow.

It may help to seed small grains at the higher rate in fields where wireworms have been identified. This can help to compensate for losses from feeding.

Cereals are generally seeded at ½-2 inches deep, and growers will sometimes seed even deeper than 2 in. Thinking of wireworm behavior, I recommend seeding at the shallower end to keep your crop ahead of the pest. Worms move up in the soil profile as conditions warm so shallow-seeded crops that can emerge and establish quickly have an advantage.

*Worms move down in the soil profile as the season advances, as temperatures exceed 20°C. They will also move up and down the soil profile in response to moisture and can be difficult to track down during hot, dry periods.

Use a seed treatment for suppression. Once the crop has established you can’t do much to protect it from wireworms, so at a minimum, you’ll want to apply an insecticide seed treatment.